一种负加速度值可变的柴油机凸轮型线研究

Study of a Diesel Engine Cam Profile Model with Adjustable Negative Acceleration

针对高负荷内燃机凸轮顶点接触应力过大的问题,提出一种由正弦、摆线、直线等多种形式函数复合而成的凸轮型线数学模型(FB3)。通过对型线模型可变参数的调整,使得型线第二、第三负加速段曲线形状和斜率发生改变,以减小负加速度值并降低凸轮顶点处接触应力。运动学、动力学仿真分析表明:FB3凸轮型线可以自由改变凸轮顶点局部负加速度值,在保持良好的流体动力润滑特性和凸轮顶点接触应力可调性的同时,可以兼顾运动曲线丰满系数、正加速度峰值等关键性能。

Aimed at a problem of too large contact stress on cam vertex of the camshaft of a high-loaded internal combustion engine,a new cam profile mathematic model（FB3）,which is composed of various functions of sine,cycloid and straight,was put forward.By adjusting the variable parameters of the profile model,the shapes and slopes of the second and the third parts of negative acceleration were changed so as to achieve the goals of reducing negative acceleration and lowering the contact stress on the cam vertex.Simulation analyses of kinematics and dynamics suggest that the FB3 cam profile can be free to change the negative acceleration around the cam vertex.While maintaining good hydrodynamic lubrication characteristics and adjustability of contact stress on the cam vertex,the FB3 cam profile can give a good balance among key performance parameters such as the fullness coefficient of cam profile and the peak value of positive acceleration.